1981 gs-550t

[doggies]

This seems strange has anyone encountered this before. I have the bike running on three cylinders only. At an idle I am getting spark on cylinder 1-2-3-4 when I increase idle or throttle up the bike at all I loose spark at number three cylinder. The bike has a 4into 1 header which was on it when purchased. I relaced the fuel petcock because the rubber check was mush. New fuel and vacuum lines. New plugs. I have jumped this bike numerous times and had charged the battery. Battery is putting out about 13.4 volts with lights on. Any help would be great. I know one of the ign. coils was changed because it says good painted on it. That's about it. I did not disassemble the carbs.

[chef1366]

Switch the spark plug cap and see if the trouble follows.

[BassCliff]

Hi,

I've got one thought. How about new plug caps?


Now I'll have to find another thought somewhere.




Thank you for your indulgence,

BassCliff

[chef1366]

http://philadelphia.craigslist.org/wan/902471446.html

[BassCliff]

Hey Bill, you're a little quicker with the clicker tonight. I thought you might go deeper though. I'm still learning about these here motorsickle things.

Hey Mr. doggies, keep us informed.


Thank you for your indulgence,

BassCliff

[chef1366]

Both coils are firing so that means the crank trigger works as is the igniter.
Puts it on the wires or spark plug caps.
Deep enough?

[waltfen]

How can it lose spark on 3 when 2 works fine? If this is the correct info then the HT lead or cap leading to 3 is broken.
My 550 always started on 3 cylinders and took an age to warm number 4 up.
I listened to the experts on this site then I checked and adjusted the valve clearances and cleaned the carbs.
Bike starts and runs like a dream now.

[Nessism]

Unless all the maintenance work on the bike is up to snuff like waltfen says, the bike will continue to run poorly for one reason or another.

You need to build a baseline by doing basic work: rebuild the carbs with fresh O-rings inside the carbs and on the intake boots, adjust the valves, clean the air filter, change the plugs, check the charging system (use the stator papers), etc.

After this work is done, you can hone in on problems much easier since you know what the problem can't be.

Don't do maintenance work and wait til the bike breaks down, and it will, and you are just guessing at what the problem will be.

Good luck.

[catbed]

plug caps. and you said it came with a header. was it properly rejetted?

[ned37]

how did you determine there is no spark on 3?

[doggies]

No Spark

What I did was pull #3 plug and hold it against the head while it was running. Today I switched caps after trying to start it. I cut some plug wire off and re attached. The plug got spark but I noticed they are always carbon black and they are fresh plugs stock heat range. I clean them off with my plug blaster but they get black again. Now when I got the bike it had a header 4into 1 on it would this make a differance if the carbs were not rejetted. I really don't want to go through all that. The bike sounds good with it and is quick as well when firing on all four. Open for suggestions. Have no touched the carbs. at all.

[Larry D]

[quote=doggies;916336]What I did was pull #3 plug and hold it against the head while it was running. Today I switched caps after trying to start it. I cut some plug wire off and re attached. The plug got spark [quote]

Are you getting a good spark now at any RPM ?

If so, that's great! Probably should give the carbs a good cleaning by using this guide.

http://thegsresources.com/gs_carbrebuild.htm

One step at a time..........

[Griffin]

What I did was pull #3 plug and hold it against the head while it was running. Today I switched caps after trying to start it. I cut some plug wire off and re attached. The plug got spark but I noticed they are always carbon black and they are fresh plugs stock heat range. I clean them off with my plug blaster but they get black again. Now when I got the bike it had a header 4into 1 on it would this make a differance if the carbs were not rejetted. I really don't want to go through all that. The bike sounds good with it and is quick as well when firing on all four. Open for suggestions. Have no touched the carbs. at all.

You HAVE to go through the carbs, or you'll likely never get it running right. There are no shortcuts. There is a step by step, logical procedure for getting these old bikes running good as new. If you don't want to bother with "all that", sell it and get something newer.

[doggies]

Carb. rebuild

Got spark on all 4 where is the best place to get carb. parts for an 81' GS550

[Griffin]

Got spark on all 4 where is the best place to get carb. parts for an 81' GS550

Now yer talkin'....

Actually, you probably won't need any parts for the carbs other than o-rings. You'll just need to completely dismantle them, thoroughly dip and clean them, then correctly reassemble them with a new o-ring set from Robert Barr. http://www.cycleorings.com/

There is an excellent tutorial linked from the main page of this site that walks you through it step by step.